1. Field of the Invention
This invention relates to a developer detecting device for detecting the condition of a developer which develops latent images.
2. Description of the Prior Art
In a copying apparatus wherein the latent image of an object to be copied is developed by the use of a developer and transferred to recording paper, judgment as to the deficiency or the like of the developer relative to a predetermined amount has been made directly in correspondence with the output of a toner sensor for determining whether the amount of developer has reached the predetermined amount and no special processing has been carried out.
However, as the amount of developer decreases and approaches a threshold level, the output of the toner sensor becomes unstable and, with the conventional system, there has occurred an inconvenience that in spite of the fact that a predetermined amount of developer is actually present, a deficiency in the amount of developer is nevertheless judged and displayed. Particularly, in a copying apparatus provided with a periodically moving developer stirring rod, when the amount of developer is small, the developer moves with the movement of the stirring rod and the amount of developer in the region in which the toner sensor is disposed increases or decreases, and this has led to the inconvenience of a periodic display of deficiency of the developer.
Also, in a copying apparatus having a toner sensor using a piezoelectric vibrator, in some cases, the toner sensor has malfunctioned due to temporary vibration of the machine and a deficiency of developer has been judged even when there is a sufficient amount of developer, and such judged deficiency of developer has been displayed.